The present application relates to artificial lighting systems. It finds particular application when used in conjunction with organic light emitting diodes (OLEDs) and will be described with particular reference thereto. It is to be understood, however, that it is also applicable to applications that use silicon based diodes, or other inorganic semiconductors, and is not necessarily limited to the aforementioned application.
Incandescent lamps have found wide range success in the lighting industry, meeting a wide range of commercial demands. The incandescent lamp, however, does have several drawbacks that make it unsuitable for certain applications. For instance, the filament generates a substantial amount of heat, and the vacuum chamber that encapsulates the filament occupies a substantial amount of space. Additionally, incandescent filaments can be easily damaged, as they are sensitive to shock and vibration. Thus, it is impractical or impossible to use incandescent lamps for certain applications.
Light emitting diodes (LEDs) have demonstrated that they are a viable alternative to incandescent lamps in conventional roles, and can fulfill additional lighting roles where incandescent lamps cannot. LEDs have a robust, compact structure that makes them ideal for applications with space constraints, and applications prone to mechanical shock and vibration.
With such a stress in the industry on space savings, (e.g. cell phones, PDAs, laptops, flat panel displays, and the like) smaller is better. Even though the LEDs themselves are small, durable, and dissipate relatively little power, additional space is required by circuitry that supports the LED. Typically, the source current is much greater than the operating current of the LED. To limit the current to the LED, resistors are typically used to limit the current by dissipating energy, also generating heat. Resultantly, additional space is needed to provide adequate cooling for the circuit components.
Also typical is the use of planar magnetics in conventional LED supporting circuitry. A planar magnetic implementation uses a high frequency power converter that causes electromagnetic interference. Bulky filters are then used to suppress the interference generated by the power converter. Both the inductors used in the planar magnetics and the filters add bulk to the LED supporting circuitry.